Methods of enzymology, chemical and enzymatic kinetics, and synthetic and analytical chemistry are being used to develop novel agents targeted against the reverse transcriptase (RT) and protease enzymes of HIV-l. i) Design of a convenient continuous spectral assay for RT is being investigated. ii) Affinity labeling agents and/or mechanism-based inhibitors are being developed to probe the active site of RT. Nucleoside analogs that contain functional groups, including an epoxide and a carbonyl group, that are potentially capable of reacting with nucleophiles at the active site of RT have been prepared and tested for anti-HIV activity in vitro. iii) Available information suggests that the HIV protease is an aspartyl protease. Syntheses of potential inhibitors for this class of protease are underway, and several such compounds have been tested for anti-HIV activity. iv) Three natural products derived from South Pacific marine sponges have been tested against HIV in cell culture. Although none of the compounds tested to date have exhibited anti-HIV activity in vitro, they are potentially useful as enzyme inhibitors and may yield valuable information concerning the active sites of the target enzymes.